Injection nozzle system

ABSTRACT

A nozzle system is provided comprising a nozzle tip supported in a nozzle body with an alignment member. The alignment member has a connection for engaging a corresponding connection located on the nozzle body. The alignment member also has an aperture concentric with the sleeve that has a tapered engagement surface for contacting a tapered engagement surface on the nozzle tip. A first melt channel is defined through the nozzle body and a second melt channel is defined through the nozzle tip. The melt channel in the nozzle tip has a first section that extends along a first axis from an inlet, a second section that extends from the first section at an incline and a third section that extends from the second section parallel to and eccentric with the first axis. The resulting melt channel defines a straight through channel parallel to said first axis from said inlet to said opening.

FIELD OF THE INVENTION

The present invention relates to injection molding and in particular toan injection nozzle system.

BACKGROUND OF THE INVENTION

Temperature control of the melt as it exits the tip of an injectionnozzle is often critical to successful injection molding. If thetemperature rises too high degradation of the melt will result and ifthe temperature falls too low the melt will clog up the system.

One approach to controlling the temperature of the melt at the tip ofthe nozzle is to divert the melt so that it exits the nozzle tip from aside opening (see for example U.S. Pat. No. 5,658,604 (Gellert)). Themelt then collects in a gathering space surrounding the tip before itpasses through the mold gate. The advantage of this approach is that theresulting greater mass of the tip below the side opening improves heattransfer from the tip to the melt collecting in the gathering space. Aproblem with this approach is that the diversion of the melt effects theeven flow of the melt through the system. Also, the diversion through aside opening introduces the melt to relatively cooler surfaces of themelt plate that tend to cool the melt excessively.

It is also important that the nozzle tip be located accurately withinthe nozzle body to ensure that the respective melt channels align.

Slight variances in the diameters of the nozzle tips and the bores ofthe nozzle bodies, or in the thread engagement between the nozzle bodyand nozzle tip, can lead to slight misalignments of the respective meltchannels. Such misalignments can negatively effect the flow of meltthrough the nozzle.

SUMMARY OF THE INVENTION

The present invention provides an improved nozzle system that overcomesthe problems discussed above.

In one aspect, the invention provides a nozzle tip for an injectionmolding machine, said nozzle tip comprising:

a body having a first portion and a second portion;

a melt channel extending from an inlet defined in said first portion toan opening defined in said second portion, a first section of said meltchannel extending from said inlet along a first axis, a second sectionof said melt channel extending from said first section along a secondaxis that is inclined relative to said first axis and a third section ofsaid melt channel extending from said second section along a third axisthat is parallel to and eccentric from said first axis, wherein astraight through channel is defined in said melt channel parallel tosaid first axis from said inlet to said opening.

In another aspect, the invention provides a nozzle system for aninjection molding machine, said nozzle system comprising:

a nozzle body defining a first melt channel and a bore along a commonaxis, said nozzle body having a first connector;

a nozzle tip defining a first portion sized to fit in said bore and asecond portion for protruding from said bore, said nozzle tip defining asecond melt channel;

a first tapered engagement surface defined on said second portion ofsaid nozzle tip; and

an alignment member having a cylindrical sleeve with a second connectorfor releasably connecting said alignment member to said first connectorof said nozzle body, said alignment member defining an aperture coaxialwith said cylindrical sleeve, said aperture having a second taperedengaging surface for engaging said first tapered engaging surface onsaid nozzle tip to locate said nozzle tip in said nozzle body with saidfirst and second melt channels aligned along said common axis.

DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show moreclearly how it may be carried into effect, reference will now be made byway of example to the accompanying drawings. The drawings show preferredembodiments of the present invention, in which:

FIG. 1 is a partial cross sectional view of a nozzle system inaccordance with the present invention;

FIG. 2 is an exploded cross sectional view of the nozzle system of FIG.1;

FIGS. 3(a)-(p) are transverse sectional views of the nozzle tip of FIG.1; and

FIG. 4 is a partial cross sectional view of a nozzle system inaccordance with a second embodiment of the present invention.

FIG. 5 is a partial cross-sectional view of a nozzle system inaccordance with the present invention, the system being utilized with adirect sprue gate;

FIG. 6 is a partial cross-sectional view of a nozzle system inaccordance with the present invention, the system being utilized with ahot valve gate; and

FIG. 7 is a partial cross-sectional view of a nozzle system inaccordance with the present invention, the system being utilized with acylindrical valve gate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2, an injection nozzle system in accordancewith the present invention is shown generally at 10. The nozzle system10 includes a nozzle body 12, a nozzle tip 14 and an alignment member16.

The nozzle system 10 is used with an injection molding machine (notshown) such as is shown and described in U.S. Pat. No. 5,658,604(Gellert) which is hereby incorporated by reference.

Nozzle body 12 has an end 18 that defines a bore 20 along channel axis22 for receiving the nozzle tip 14. A melt channel 24 is defined in thenozzle body 12 and opens at the bore 20. Electric heating element 26extends adjacent to the outer circumference of the nozzle body 12 and issupported by a holder 28 which is part of the nozzle body 12. A firstconnector 30 is disposed on the circumference of the nozzle body 12.Preferably, first connector 30 is an external thread however othersuitable connecting means may be utilized. For instance, first connector30 could be a rotatable collar defining an internal thread forconnecting with a corresponding threaded element as described furtherbelow.

Nozzle tip 14 has a first portion 32 that is sized to fit within thebore 20 of the nozzle body 12. Nozzle tip 14 also has a second portion34 that protrudes from the end 18 of the nozzle body 12. Second portion34 defines an outer engagement surface 36 that has opposing taperedwalls and is preferably frusto-conical. The configuration of the secondportion 34 below the outer engagement surface 36 is preferably conicalending in apex 37. A melt channel 38 is defined through nozzle tip 14from the first portion 32 to the second portion 34. Melt channel 38 ofnozzle tip 14 aligns with melt channel 24 of nozzle body 12 to permitthe flow of pressurized melt from the nozzle body 12 to the nozzle tip14. An opening 40 in the second portion 34 allows melt to pass from thenozzle tip 14 to a gathering space 42 defined in a mold plate 44 whereit collects before entering a mold gate 46.

Alignment member 16 has a second connector 48 disposed on sleeve 50 toconnect with first connector 30 to secure the nozzle tip 14 to thenozzle body 12. Second connector 48 is preferably an internal threaddefined on the inner surface of sleeve 50 however other suitableconnecting means may be utilized. For instance, second connector 48 maybe an external thread defined on the outer surface of sleeve 50 tothreadably engage with the rotatable collar type of first connector 30on nozzle body 12 as described above.

A hexagonal flange 52 is disposed on the alignment member 16 tofacilitate tightening or loosening the connection of alignment member 16with the nozzle body 12. A sealing flange 54 is disposed on thealignment member 16 for contacting mold plate 44 to form a seal againstpressurized melt leaking from the gathering space 42 to adjacent partsof the molding machine. Sealing flange 54 has an abutment face 56 thatabuts against the surface of the mold plate 44 to form the desired seal.

Alignment member 16 also includes an aperture 57 defining an innerengagement surface 58 sized to receive second portion 34 of nozzle tip14 and engage outer engaging surface 36. Inner engaging surface 58 hasopposing tapered walls and is preferably frusto-conical. Innerengagement surface 58 is coaxial with sleeve 50 so that inner engagementsurface 58 will be coaxial with bore 20 and melt channel 24 whenalignment member 16 is mounted to nozzle body 12.

In use, inner engagement surface 58 of alignment member 16 engages outerengagement surface 36 of nozzle tip 14 to concentrically align meltchannel 38 of nozzle tip 14 with melt channel 24 of nozzle body 12.

Referring to FIGS. 3(a)-(p), the structure of melt channel 38 definedthrough nozzle tip 14 may be better understood. Melt channel 38 has afirst section 60 that extends along channel axis 22 through firstportion 32 of nozzle tip 14. First section 60 decreases in crosssectional area from an inlet 62 to the beginning of second section 64.Second section 64 extends diagonally from channel axis 22 to thirdsection 66. The cross sectional area of second section 64 remainsrelatively constant along its length. The upper wall 67 of the secondsection 64 terminates at the upper periphery of the opening 40. Thirdsection 66 extends parallel to channel axis 22 to opening 40.

The channel wall 68 of third section 66 is located nearer to channelaxis 22 than is the channel wall 70 of first section 60. Accordingly, athrough channel 72 is defined parallel to channel axis 22 from inlet 62to opening 40. Through channel 72 improves the flow of melt through meltchannel 38 and reduces the occurrence of pressure drops. Through channel72 also reduces heat losses in the melt as it enters the gathering space42 by directing more melt centrally adjacent to the hotter nozzle tip 14and less melt eccentrically towards cooler surfaces of the nozzle system10 and mold plate 44. The structure of melt channel 38 thus optimizesthe heat transfer provided by exposing the surface of the melt to thelarger mass of the nozzle tip 14 with the reduced heat losses providedby directing melt away from cooler parts of the apparatus.

Referring to FIG. 4, a second embodiment of nozzle system 10 inaccordance with the present invention is shown. Those elements of thenozzle system 10 that correspond with elements of the first embodimentof nozzle system 10 described above are assigned the same referencenumerals and are not described in detail below.

The nozzle system 10 includes the same structure of nozzle body 12 andnozzle tip 14 as described above combined with a modified alignmentmember 16′. The modification to the alignment member 16′ consists of theaddition of an integral housing 74′ defining a mold gate 76′. Theintegral housing 74′ has a cavity that defines a gathering space 42′ forcollection of pressurized melt prior to it passing through mold gate76′. Abutment face 56′ is defined on the outer surface of housing 74′for contacting mold plate 44 to form a seal against pressurized meltleaking from the gathering space 42′ to adjacent parts of the moldingmachine.

The nozzle system 10 of the present invention is not limited to use withmold gates. The nozzle system 10, and in particular the alignmentstructures of the nozzle tip 14 and alignment member 16, 16′, may beincorporated in a variety of alternative gate applications to accuratelylocate the respective melt channels 24 and 38.

The nozzle system 10 is made of materials having relatively high thermalconductivity. Nozzle body 12 and alignment member 16, 16′ are preferablyformed from titanium, H-13 or other suitable materials that may beobtained and manufactured at reasonable costs. Nozzle tip 14 ispreferably formed of tungsten carbide due to its superior heat transferproperties although other thermally conductive materials may beutilized.

The above described embodiments of the invention are intended to beexamples of the present invention and alterations and modifications maybe effected thereto, by those of skill in the art, without departingfrom the scope of the invention which is defined solely by the claimsappended hereto.

We claim:
 1. A nozzle system for an injection molding apparatus, saidnozzle system comprising: a nozzle body (12) defining a first meltchannel (24), said first melt channel capable of communicating with asource of pressurized melt, a nozzle tip (14), and an alignment member(16) for retaining said nozzle tip within said nozzle body, said nozzletip (14) having a first portion (32) and a second portion (34), saidnozzle tip (14) defining a second melt channel (38), said second meltchannel (38) extending from an inlet (62) adapted to communicate withsaid first melt channel (24) to an opening (40) defined in an end ofsaid nozzle tip (14), said opening (40) adapted to communicate with amold cavity having a gate, said second melt channel (38) having a firstsection (60) defined in said first portion (32), a second section 64 andthird section (66) defined in said second portion (34), said firstsection (60) extending from said inlet along a first axis (22), saidthird section (66) communicating with said first section (60) throughsaid second section (64) and extending to said opening (40) along asecond axis, said second axis being offset from said first axis (22)said second section being inclined with respect to said first sectionand with respect to said third section, and wherein a straight throughchannel (72) offset from said first axis (22) is provided by said first,second and third sections of said second melt channel (38) from saidinlet (62) to said gate.
 2. The nozzle system of claim 1 wherein saidthrough channel (72) is parallel to said first axis (22).
 3. The nozzlesystem of claim 1 wherein said second axis is parallel to said firstaxis (22).
 4. The nozzle system of claim 1 wherein said first portion(32) has a first portion wall (70), and said second portion (34) has asecond portion wall (68) disposed closer to said first axis (22) thansaid first portion wall (70).
 5. The nozzle system of claim 4 whereinsaid second portion wall (68) is substantially parallel to said firstaxis (22).
 6. The nozzle system of claim 4 wherein said second axis isparallel to said first axis (22).
 7. A nozzle system as claimed in claim1 wherein said second portion (34) is generally conical.
 8. A nozzlesystem as claimed in claim 1 wherein said second portion (34) has anouter engagement surface that is generally frusto-conical.
 9. A nozzlesystem tip as claimed in claim 1, wherein said second portion (34) isgenerally conical below said outer engagement surface.
 10. A nozzlesystem tip as claimed in claim 9, wherein said opening (40) is definedabove the apex (37) of said generally conical second portion.
 11. Anozzle system according to claim 1 wherein said nozzle body has a firstconnector (30); said nozzle tip (14) including a first taperedengagement surface (36) defined on said second portion (34); and saidalignment member (16) having a cylindrical sleeve with a secondconnector for releasably connecting said alignment member to said firstconnector of said nozzle body, said alignment member defining anaperture coaxial with said cylindrical sleeve, said aperture having asecond tapered engaging surface for engaging said first tapered engagingsurface on said nozzle tip to locate said nozzle tip in said nozzlebody.
 12. A nozzle system as claimed in claim 11, wherein at least oneof said engagement surfaces is frusto-conical.
 13. A nozzle system asclaimed in claim 12, wherein a hexagonal flange (52) is located on saidalignment member concentrically with said sleeve to permit tightening orloosening of said threaded sleeve on said threaded nozzle body.
 14. Anozzle system as claimed in claim 13, wherein an abutment face (56) islocated on said alignment member for sealing a gathering space adjacentto said nozzle tip.
 15. A nozzle system as claimed in claim 13, whereinsaid alignment member (16) includes a housing (74′) that defines a moldgate concentric with said nozzle tip.